For downlink demodulations, Long Term Evolution (LTE) specifications define demodulation reference signals (DMRSs) to enable UEs to estimate the reference signals and derive channel equalizers for data equalization and channel decoding. The DMRSs may be carried in specific resource elements (REs) in each slot and the location of the REs may be specifically determined according to antenna configurations (or transmission modes). For different antenna ports, different REs for carrying the DMRSs are used with different orthogonal cover code (OCC) schemes, resulting in different overhead, and different channel estimation accuracy.